---
title: "Molecular Shapes from Electron Pair Repulsion"
description: "Electron pairs around a central atom push each other as far apart as they can, and that alone predicts the shape. A lone pair pushes harder than a bonding pair, which is why water is bent and not stra"
canonical: https://lightmysky.com/learn/science/molecular-shapes-from-electron-pair-repulsion-mt_Of6ZxYjOsn
source: https://lightmysky.com/learn/science/molecular-shapes-from-electron-pair-repulsion-mt_Of6ZxYjOsn.md
retrieved: 2026-09-12
---

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# Molecular Shapes from Electron Pair Repulsion

Electron pairs around a central atom push each other as far apart as they can, and that alone predicts the shape. A lone pair pushes harder than a bonding pair, which is why water is bent and not straight.

Subject: Science · Area: Matter & Materials · Ages 15 to 16
Page: https://lightmysky.com/learn/science/molecular-shapes-from-electron-pair-repulsion-mt_Of6ZxYjOsn

## Ready when they can

- Predict the shape and bond angle of a simple molecule from the number of bonding and lone pairs
- Explain why ammonia and water have smaller bond angles than methane
- Draw a three-dimensional representation using wedges and dashes rather than a flat sketch

## Lesson: Pairs push shapes into place

Electron pairs around a central atom push each other as far apart as they can. Count the bonding plus lone pairs and you can predict the shape and its angles. Sketch the Lewis structure first, since dots and lines give you the pair count.

**Example.** Methane has four bonding pairs and no lone pairs, giving a tetrahedron with angles near 109.5 degrees. Draw it in 3D: a solid wedge means a bond coming out at you, and a dashed line means one going back. Never settle for a flat sketch.

A lone pair pushes harder than a bonding pair. Ammonia carries one lone pair, so its angle shrinks below methane. Water carries two, so it bends tighter still. Single, double and triple bonds each count as one direction when you count. If your sketch and your pair count disagree, recheck the Lewis structure first.

**Tip.** Work every shape the same way. Draw the Lewis structure, count pairs around the central atom, then pick the shape. If your sketch and your pair count disagree, recheck the Lewis structure first.

**Recap.** Draw pairs first, count them next, and let lone pairs squeeze the shape you sketch in 3D.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Dot-and-Cross Diagrams and Lone Pairs](https://lightmysky.com/learn/science/dot-and-cross-diagrams-and-lone-pairs-mt_ghK4a25usP)

## Opens up

- [Electronegativity and the Polar Bond](https://lightmysky.com/learn/science/electronegativity-and-the-polar-bond-mt_TwSlh2VvUT)